diff --git a/Api/TpayInterface.php b/Api/TpayInterface.php
index a18b0b3..264794e 100644
--- a/Api/TpayInterface.php
+++ b/Api/TpayInterface.php
@@ -32,6 +32,8 @@ public function getApiKey(): ?string;
 
     public function getSecurityCode(): ?string;
 
+    public function getOpenApiClientId(): ?string;
+
     public function getOpenApiSecurityCode(): ?string;
 
     public function getMerchantId(): ?int;
diff --git a/Model/ApiFacade/Transaction/TransactionApiFacade.php b/Model/ApiFacade/Transaction/TransactionApiFacade.php
index c750cd5..1281c43 100755
--- a/Model/ApiFacade/Transaction/TransactionApiFacade.php
+++ b/Model/ApiFacade/Transaction/TransactionApiFacade.php
@@ -96,7 +96,7 @@ private function createOriginApiInstance(TpayInterface $tpay)
     private function createOpenApiInstance(TpayInterface $tpay)
     {
         try {
-            $this->openApi = new OpenApi($tpay->getClientId(), $tpay->getOpenApiPassword(), !$tpay->useSandboxMode());
+            $this->openApi = new OpenApi($tpay->getOpenApiClientId(), $tpay->getOpenApiPassword(), !$tpay->useSandboxMode());
             $this->openApi->authorization();
             $this->useOpenApi = true;
         } catch (Exception $exception) {
diff --git a/Model/Tpay.php b/Model/Tpay.php
index b5c8c63..c12805c 100755
--- a/Model/Tpay.php
+++ b/Model/Tpay.php
@@ -219,9 +219,9 @@ public function getMerchantId(): ?int
         return (int) $this->getConfigData('merchant_id');
     }
 
-    public function getOpenApiClientId()
+    public function getOpenApiClientId(): ?string
     {
-        return $this->getConfigData('open_api_client_id') ?? '';
+        return $this->getConfigData('open_api_client_id');
     }
 
     public function getSecurityCode(): ?string